Inside Webmaster Tools is “Fetch” tool. It allows you to submit any page to Google. You can then also have Google index the page. When you fetch a time stamp is recorded and a full HTML copy of the page too.
I am not sure if Google uses this to prove which is the original copy. Most website owners don’t know this exists. So it’s hard to use it as proof of the original, because the original creator may not even use the tool.
However, if everyone started to submit key articles, then it theoretically could compare the two fetches and decide which is earlier. It could be automated too with sitemap uploads as you post content.
Moreover, you could then use this as evidence in a DMCA take down that your copy is the earliest. Anyways, there are ways to prove earliest content.
That's my point. There is no way to verify the date assertion of an arbitrary page.
The problem is akin to standing in a crowd where some people hold a sign with their age on it and others do not hold a sign, then trying to verify the age of an arbitrary people.
You can prove in many ways that your content existed at a given time. But it seems quite impossible to prove that a copy of it didn't exist earlier somewhere else.
edit: unless the content itself contains a proof like the latest block hash or something like that, but that could be edited
Yes, this appears to be the date google shows next to the search results.
Every time I write a blog post, I submit manually via webmaster tools "Fetch as Google" so that it gets indexed immediately. That way, the date google shows matches the date I published the article.
I am not sure if Google uses this to prove which is the original copy. Most website owners don’t know this exists. So it’s hard to use it as proof of the original, because the original creator may not even use the tool.
However, if everyone started to submit key articles, then it theoretically could compare the two fetches and decide which is earlier. It could be automated too with sitemap uploads as you post content.
Moreover, you could then use this as evidence in a DMCA take down that your copy is the earliest. Anyways, there are ways to prove earliest content.